Actually that would be that a few patients have transmitted AIDS to their dentists. ...And that is why dentists now wear masks and goggles whereas in the 60,70’s they didnt.
Although it is possible for a dentist to cut his hand and transmit it to the patient also.
Exposure to blood.
dentist gives patients aids
http://aids2012.ucsf.edu/2012/07/19/how-the-aids-epidemic-changed-the-dental-profession-in-the-1980s/
http://www.huffingtonpost.com/2013/03/28/-w-scott-harrington-hiv-dentist-hepatitis-expose-patients_n_2974053.html
W. Scott Harrington, Oklahoma Dentist, May Have Exposed 7,000 Patients To HIV Or Hepatitis
http://www.deseretnews.com/article/240576/LAWSUIT-SAYS-FLORIDA-DENTIST-GAVE-AIDS-TO-A-6TH-PATIENT.html
http://www.dailymail.co.uk/news/article-2173095/Thousands-patients-risk-HIV-dodgy-Denver-dentist-REUSED-syringes-12-years.html
http://www.cdc.gov/mmwr/preview/mmwrhtml/00001679.htm
http://www.jpost.com/Israel/Dentist-involved-in-AIDS-case-commits-suicide
http://www.independent.co.uk/news/uk/dentist-killed-by-aids-may-have-infected-patients-1567451.html